Thanks for the quick response.
But All I want to do is select from the database and give it a meaningful name [I might export this to Excel or send this to some client via Email, it doesn't matter]. I can understand if Database has restriction while putting it in, but while displaying records I was hoping it should not have any problem. But Oracle can be so stingy sometimes :-)

Come to think of it, why Oracle has a 30 character limit on object names [I know it should have some limit, but why 30 character limit] who came up with that number? just curious

Tom,

You said "do you see how many things would suddenly BREAK completely?"

Why would existing apps would break if the limit is pushed to, say 50. I guess, I did not get your point correctly. Can you help me understand? My feeling is existing (coded with limit 30) would continue as-is, and new code will choose bigger length - and why would there be any conflict?

I ran into this oracle error when converting a valid/working mysql query to oracle 10.x. Nearly every article or KB regarding ORA 00972 indicates this error is due to a column identifier in excess of 30 characters.

I found that is NOT always the case! In my case, my SELECT statements had a WHERE clause like this:
WHERE
Field_Name="A String of text goes here"

The problem was not the length of the Field_Name, but rather due to the fact that I mistakenly used double quotes instead of single quotes in my query. After I modified my query to appear as shown below, it worked:
WHERE
Field_Name='A String of text goes here'

Hopefully other people will see this and be saved some of the pain that I went through!

The URL in question is http://asktom.oracle.com/pls/apex/f?p=100:11:0::::P11_QUESTION_ID:2684299700346560644

ops$tkyte%ORA11GR2> select * from dual where "not valid" = 'x';
select * from dual where "not valid" = 'x'
                         *
ERROR at line 1:
ORA-00904: "not valid": invalid identifier

ops$tkyte%ORA11GR2> create table t ( "not valid" int );

Table created.

ops$tkyte%ORA11GR2> select * from t where "not valid" = 0;

no rows selected

ops$tkyte%ORA11GR2>

this is very helpful as matt was saying it is not always with the identifier length the query errored out but sometimes with " double quotes also it shows the same error message.

Im extracting data using a database link from a MSSQL database where one table is 31 characters long. The MSSQL table is case sensitive, so I am forced to use the "" characters.

select * from "ThisLongTableNameIsTooLongToUse"@myDBLink

returns

ORA-00972: identifier is too long

If I am reading this article correctly, there is no way to extract data from the table?

Could you PLEASE explain to me why this select command is too long!? Where is it!? Thank you!

if (OraCmd.Parameters.Contains("@p1")) OraCmd.Parameters["@p1"].Value = tbNumber.Text;
else OraCmd.Parameters.Add("@p1", tbNumber.Text);
OraCmd.CommandText = @"select
uadism.num_dism as ""allowanceNumber"",
uadism.dat_dism as ""allowanceDate"",
uadism.num_reg as ""bIdentifier"",
uadism.nam_cust as ""bName"",
uadisd.lin_dism as ""SequenceNumber,
uadisd.num_invm as ""InvoiceNumber"",
uadisd.dat_invm as ""InvoiceDate"",
uadisd.nam_item as ""Description"",
uadisd.qty_item as ""Quantity"",
codd.content as ""Unit"",
uadisd.prs_dism as ""UnitPrice"",
uadisd.amt_dism as ""Amount"",
uadisd.tax_dism as ""Tax"",
uadisd.tax_type as ""TaxType""
from uadism,uadisd,deld,codd
where
uadism.num_dism = :p1 and
uadism.num_dism = uadisd.num_dism and
deld.num_del = uadisd.num_del and
deld.lin_del = uadisd.lin_del and
codd.code_id = 'CODUNI' and
codd.code = deld.unt_poc
order by uadism.num_dism,uadisd.lin_dism";

Thank you for the explanations. I recently upgraded from 12.1 to 18.5, but I still can't use identifiers (column names) greater than 30 characters. (I don't really need to, but it got me wondering why)

SQL> create table testid ("LongestBillingBillProjectRecordStagingKey" varchar2);
create table testid ("LongestBillingBillProjectRecordStagingKey" varchar2)
                     *
ERROR at line 1:
ORA-00972: identifier is too long


SQL> create table testid (LongestBillingBillProjectRecordStagingKey varchar2);
create table testid (LongestBillingBillProjectRecordStagingKey varchar2)
                     *
ERROR at line 1:
ORA-00972: identifier is too long


SQL> desc dba_tab_columns;
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OWNER                                     NOT NULL VARCHAR2(128)
 TABLE_NAME                                NOT NULL VARCHAR2(128)
 COLUMN_NAME                               NOT NULL VARCHAR2(128)
 DATA_TYPE                                          VARCHAR2(128)
 DATA_TYPE_MOD                                      VARCHAR2(3)
 DATA_TYPE_OWNER                                    VARCHAR2(128)
 DATA_LENGTH                               NOT NULL NUMBER
 DATA_PRECISION                                     NUMBER
 DATA_SCALE                                         NUMBER
 NULLABLE                                           VARCHAR2(1)
 COLUMN_ID                                          NUMBER
 DEFAULT_LENGTH                                     NUMBER
 DATA_DEFAULT                                       LONG
 NUM_DISTINCT                                       NUMBER
 LOW_VALUE                                          RAW(32767)
 HIGH_VALUE                                         RAW(32767)
[...]

SQL> create table testid ("LongestBillingBillProjectRecordStagingKey" varchar2(10));

Table created.